Summary:
Several strains of bacteria are able to utilize malonate as sole source of carbon and energy. The key reaction in the pathway is the decarboxylation of malonate to acetate, which is catalyzed by malonate decarboxylase. Malonate is a rather inert compound, and its decarboxylation under physiological conditions requires an activation step, in which malonate forms a thioester derivative.

Malonate decarboxylase is an enzyme complex composed of three subunits, one of which is a dedicated acyl-carrier protein (acp). The acp protein is synthesized in an apo form, and is converted to its holo form by the covalent binding of the prosthetic group 2'-(5''-phosphoribosyl)-3'-dephospho-CoA to a serine residue. This prosthetic group is very unusual and the only other enzyme known to use it is citrate lyase (see citrate lyase activation).